As an air conditioning system capable of heating the room, conventionally known is a system configured by connecting room heating devices such as a radiator and a fan convector to a heat source unit having a vapor compression type refrigerant circuit (for example, see Japanese Patent Application Publication Nos. 2003-50035, 2003-172523 and 2003-50050). Such an air conditioning system heats the room by heating the floor and indoor air.
In addition, as a heat source unit of such an air conditioning system, a unit having a refrigerant circuit that uses CO2 as the refrigerant is used in some cases. In such a heat source unit that uses CO2 as the refrigerant, the refrigerant temperature on a discharge side of a compressor can be increased, and therefore, for example, when an air conditioning system is configured such that the heat of a heating medium heated by a utilization side heat exchanger in the heat source unit is released into the room in the room heating devices, the temperature level that can be used for heating a room in the room heating devices can be increased. This will achieve comfortable room heating.